Reducing the Interval Between Volume Acquisitions Improves "Sparse" Scanning Protocols in Event-related Auditory fMRI
Reducing the Interval Between Volume Acquisitions Improves "Sparse" Scanning Protocols in Event-related Auditory fMRI
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DOI：
10.1007/s10548-011-0206-x
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发表时间：
2012-04-01
期刊：
影响因子：
2.7
通讯作者：
Meyer, Martin
中科院分区：
文献类型：
--
作者：
Liem, Franziskus;Lutz, Kai;Meyer, Martin
在听觉fMRI研究的背景下，已经设计了稀疏和聚类的时间抽样fMRI方案，以减少听觉扫描仪噪声的影响。在这里，我们报告了先前建立的群集采集方案的改进。该领域许多研究人员当前使用的标准过程是一项扫描协议，其中包括图像采集之间相对较长的无声暂停（因此，相对较长的重复时间或群集发出异步）；正是在这些停顿期间，刺激出现。这种方法使刺激诱导的大胆反应不太可能被扫描仪噪声引起的大胆响应掩盖。它还允许大胆的响应在基线附近下降；因此，避免了大胆信号的饱和，理论上增加了效果大小。这种方法可能的缺点是在给定时间段内可能发生的刺激呈现和图像采集数量有限，这可能导致效应大小的估计不准确（较高的标准误差）。由于尚未对这种推理线进行经验测试，因此我们决定在群集 - 帕斯斯（Sparse）协议的背景下改变群集发出异步（7.5、10、12.5和15 s）。在这项研究中，有16位健康的参与者听了口语。我们通过解剖学区域（听觉核心和关联区域）进行了全脑fMRI小组统计和感兴趣的区域分析区域。我们发现，该协议包括短簇发出异步（7.5 s），其结果比其他协议更有利，该协议涉及较长的群集发作异步。短簇发作的异步方案显示出较大的活化体素和较大的平均效应大小，标准误差较低。我们的发现表明，与先前的经验相反，短簇发作的异步是有利的，因为可以在任何给定的时期内传递更多的刺激。或者，可以在更少的时间内提出给定数量的刺激，这扩大了可能的fMRI应用。
Sparse and clustered-sparse temporal sampling fMRI protocols have been devised to reduce the influence of auditory scanner noise in the context of auditory fMRI studies. Here, we report an improvement of the previously established clustered-sparse acquisition scheme. The standard procedure currently used by many researchers in the field is a scanning protocol that includes relatively long silent pauses between image acquisitions (and therefore, a relatively long repetition time or cluster-onset asynchrony); it is during these pauses that stimuli are presented. This approach makes it unlikely that stimulus-induced BOLD response is obscured by scanner-noise-induced BOLD response. It also allows the BOLD response to drop near baseline; thus, avoiding saturation of BOLD signal and theoretically increasing effect size. A possible drawback of this approach is the limited number of stimulus presentations and image acquisitions that are possible in a given period of time, which could result in an inaccurate estimation of effect size (higher standard error). Since this line of reasoning has not yet been empirically tested, we decided to vary the cluster-onset asynchrony (7.5, 10, 12.5, and 15 s) in the context of a clustered-sparse protocol. In this study sixteen healthy participants listened to spoken sentences. We performed whole-brain fMRI group statistics and region of interest analysis with anatomically defined regions of interest (auditory core and association areas). We discovered that the protocol, which included a short cluster-onset asynchrony (7.5 s), yielded more advantageous results than the other protocols, which involved longer cluster-onset asynchrony. The short cluster-onset asynchrony protocol exhibited a larger number of activated voxels and larger mean effect sizes with lower standard errors. Our findings suggest that, contrary to prior experience, a short cluster-onset asynchrony is advantageous because more stimuli can be delivered within any given period of time. Alternatively, a given number of stimuli can be presented in less time, and this broadens the spectrum of possible fMRI applications.